code: def test_non_unique_cat(df):
      """Raise ValueError if categories is provided, but is not unique."""
      with pytest.raises(ValueError):
          df.encode_categorical(a=[1, 2, 3, 3])
  
imports: import datetime
  import numpy
  import pandas
  import pytest
  from hypothesis import given, settings
  from pandas.testing import assert_frame_equal
  from janitor.testing_utils.strategies import categoricaldf_strategy, df_strategy
label_desc: Use image node_id 13 for calling a global function with example usage: test_non_unique_cat(df) without return types